growing old; aging.
Cell Biology. (of a cell) no longer capable of dividing but still alive and metabolically active.

1650–60; < Latin senēscent- (stem of senēscēns) present participle of senēscere ‘to grow old’, equivalent to sen- ‘old’ + -ēscent- -escent

senescence, noun
unsenescent, adjective Unabridged
Based on the Random House Dictionary, © Random House, Inc. 2014.
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World English Dictionary
senescent (sɪˈnɛsənt)
1.  growing old
2.  characteristic of old age
[C17: from Latin senēscere to grow old, from senex old]

Collins English Dictionary - Complete & Unabridged 10th Edition
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Word Origin & History

1656, from L. scenescens, prp. of senescere "to grow old," from senex "old" (see senile).
Online Etymology Dictionary, © 2010 Douglas Harper
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American Heritage
Medical Dictionary

senescence se·nes·cence (sĭ-něs'əns)
The process of growing old; aging.

senescent se·nes·cent (sĭ-něs'ənt)
Growing old; aging.

The American Heritage® Stedman's Medical Dictionary
Copyright © 2002, 2001, 1995 by Houghton Mifflin Company. Published by Houghton Mifflin Company.
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Encyclopedia Britannica


in human beings, the final stage of the normal life span. Definitions of old age are not consistent from the standpoints of biology, demography (conditions of mortality and morbidity), employment and retirement, and sociology. For statistical and public administrative purposes, however, old age is frequently defined as 60 or 65 years of age or older

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Encyclopedia Britannica, 2008. Encyclopedia Britannica Online.
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Example sentences
The resulting panorama is early senescence with all of the common underlying irreversible medical conditions.
But many tumor cells can be grown indefinitely in a laboratory culture and are said to have escaped senescence.
It will eventually sigh off another shell of gas and settle into eternal senescence as a white dwarf.
Eventually they grow so short that the cells reach a state of senescence in which they simply stop dividing or die.
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